1. Field of the Invention
The present invention relates to a data communication methods and apparatus in a CDMA (Code Division Multiple Access) communication system and, more particularly, to packet data service providing methods and apparatus.
2. Description of the Related Art
In CDMA and W-CDMA (Wideband-CDMA), considered as a standard for the next generation communication system, packet data communication is implemented with one-to-one continuous connection established between a terminal and a base station. However, it is ideal that the one-to-one connection between a terminal and a base station lasts as long as packet data is exchanged and is released during a packet data communication suspension period, so that the capacity of communication channels is efficiently used and thus communication cost is saved for users.
A conventional packet data service in a CDMA communication system suffers excessive overheads due to the continuous one-to-one connection state of communication channels during a packet data service, thus decreasing use efficiency of a channel capacity and imposing increased cost on users. Moreover, the demands for data service such as PC (Personal Computer) communication, Internet access, and mobile communication-based data service are gradually increasing. Most data services are performed in the form of packet data and data is availability instantaneously rather than always being present. That is, most data communications are packet data communications.
As a result, there is a need for enabling more subscribers to access a data service at low cost by minimally modifying the conventional CDMA network interface structure.
FIG. 1 is a block diagram of a terminal (e.g., fixed or mobile subscriber station), a base station, and a radio link in a mobile communication system. The radio link of FIG. 1 is composed of a forward channel for data transmission from the base station to the terminal and a reverse channel for data transmission from the terminal to the base station.
A conventional CDMA mobile communication system has a forward channel structure as shown in FIG. 3 and a reverse channel structure as shown in FIG. 2. The forward CDMA channel has a pilot channel, a sync channel, a paging channel, and a forward traffic channel divided into a fundamental channel and a supplemental channel. The reverse CDMA channel includes an access channel and a reverse traffic channel divided into a fundamental channel and a supplemental channel.
A conventional bidirectional traffic channel has too low a bit rate to provide a packet data service. An approach to ensuring a bit rate high enough for implementing a packet data service in a conventional bidirectional traffic channel is to separate the traffic channel into a fundamental channel and a supplemental channel. The fundamental channel provides the same function of the conventional bidirectional traffic channel and the supplemental channel provides packet data communication. For a packet data service, a call is maintained between a base station and a terminal, as shown in FIG. 1 via forward and reverse fundamental channels.
FIG. 4 is a flowchart illustrating the use of channels for a conventional packet data service. Referring to FIG. 4, a basic call is set up between a terminal and a base station using a pilot channel, a sync channel, a paging channel and an access channel, in step 411. Here, the basic call is bidirectionally performed on forward and reverse fundamental channels. In step 412, the base station (terminal) determines whether a request for packet data transmission has been issued from the terminal (base station). In the absence of the packet data transmission request, the procedure jumps to step 417 in which the call is maintained on the bidirectional fundamental channels.
In the presence of the packet data transmission request in step 412, the base station (terminal) notifies the terminal (base station) of use of a supplemental channel on the forward (reverse) fundamental channel, in step 413, and the terminal (base station) sends an acknowledge signal to the base station (terminal) on the reverse (forward) fundamental channel, in step 414. In step 415, packet data is completely transmitted on bidirectional supplemental channels. Upon completion of the packet data transmission/reception, the bidirectional supplemental channels stop their action in step 416. Then, the call is maintained on the bidirectional fundamental channels, in step 417.
The above call set-up procedure will now be reviewed with respect to the terminal. A controller of the terminal obtains information on a corresponding base station via a pilot channel, a sync channel, and a paging channel among the forward channels of the base station. Information for access to the base station is generated by a message processor of the terminal, converted to a signal by a baseband processor, and transmitted to the base station on a reverse access channel.
A message processor in the base station analyses the access information received from the terminal, gets forward and reverse fundamental channels ready, and sends to the terminal a message on the paging channel indicating that the fundamental channels are ready. A message processor of the terminal obtains the forward fundamental channel, using the bidirectional fundamental channel information received from the base station. Then, the terminal sends a signal to the base station on the reverse fundamental channel in order to allow the base station to obtain the reverse fundamental channel. When the base station succeeds in obtaining the reverse fundamental channel, it notifies the terminal of the fact on the forward fundamental channel. When the base station and the terminal obtain the bidirectional fundamental channels, the call set-up is completed.
Following the call set-up on the bidirectional fundamental channels, the terminal and the base station await packet data transmission/reception, while exchanging their information on the bidirectional fundamental channels. Despite the absence of transmit/receive packet data, the call is maintained on the bidirectional fundamental channels. Packet data communication, after the call set-up, is implemented while repeating the procedure shown in FIG. 4.
FIG. 5 is a state transition diagram of a terminal on the basis of a conventional CDMA standard. Referring to FIG. 5, when power is on in a state 511, the terminal is set to an initialization state 512. If the terminal synchronizes its timing to that of a system in the initialization state 512, the terminal transits to an idle state 513. The terminal may attempt a call, the base station transmits information of the call attempt to the terminal on a paging channel, and the terminal sends a page response message to the base station, in the idle state 513. Then, the terminal is set to a system access state 514. If the terminal fails to obtain a paging channel message or is directed from the base station to a different adjacent base station in a handoff in the idle state 513, the terminal returns to the initialization state 512. Here, if the terminal succeeds in system access except for the call attempt or reception of a call acknowledge signal in the system access state 514, the terminal returns to the idle state 513. However, if the terminal succeeds in the call attempt or reception of the call acknowledge signal in the system access state 514, the terminal goes to a traffic channel state 515. The traffic channel state 515 lasts as long as traffic is processed. When traffic channels stop their action, the terminal returns to the initialization state 512.
A communication system maintains a call on bidirectional fundamental channels despite infrequent transmit/receive packets in the conventional packet data service. For example, assuming that packet data is transmitted/received for one second in about a one minute interval, the communication system remains logged on the bidirectional fundamental channels for 59 seconds even with data transmission/reception suspended. In this case, a signal transmitted on the bidirectional fundamental channels interferes with another channel, resulting in wasted capacity of another supportable service in the CDMA communication network. Furthermore, as more users demand the packet data service, the CDMA mobile communication network becomes less accessible to users confined to voice communication on fundamental channels only.
The constraint of continuous connection between the terminal and the base station for a short packet transmission/reception increases packet data communication cost and places an obstacle on wide provision of the packet data communication over the CDMA mobile communication network. As a result, the CDMA mobile communication lags behind other communication systems in competitiveness and thus is less utilized.
An object of the present invention is to provide methods and apparatus for providing a packet data service in a CDMA mobile communication system such that channels are occupied only during packet transmission/reception while a call is established.
Another object of the present invention is to provide methods and apparatus for providing packet data service such that voice and data service channels are processed independently with a new channel structure introduced.
To achieve the above and other objects, there is provided methods and apparatus for providing packet data service between a terminal and a base station in a mobile communication system. In one method and apparatus, packet data is transmitted from the terminal (base station) on a reverse (forward) packet traffic channel to the base station (terminal) during a data transmission period, the occupation of the reverse (forward) packet traffic channel is released during a data transmission suspension period; and the base station controls the reverse (forward) packet traffic channel over a packet control channel.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings in which the same reference numerals are used throughout the various figures to designate same or similar components.